What is AEB?
Automatic emergency braking, sometimes called autonomous emergency braking, monitors the vehicle’s path for a possible collision. Depending on the design and situation, it may warn the driver, increase braking support or apply the brakes.
Its purpose is to help avoid some crashes or reduce their severity. It cannot guarantee a stop, detect every hazard or make the vehicle self-driving.
How it works
AEB may use a forward camera, radar or both. Some systems are designed primarily for vehicles; others can also respond to pedestrians, cyclists, junction conflicts or reversing hazards within specified conditions.
Capabilities vary substantially by vehicle and speed. The owner’s manual describes the intended targets, operating range and limitations for your exact system.
What the driver may notice
An intervention can include:
- a dashboard or head-up warning
- an urgent sound or steering-wheel vibration
- brake preparation or increased braking assistance
- a short, firm automatic brake application
The driver should respond to the real traffic situation rather than waiting for the vehicle to act. If braking appears inappropriate, remain in control and follow the vehicle’s documented override behaviour only when the traffic situation allows it.
Common limitations
Detection may be affected by:
- rain, fog, glare, darkness or airborne dust
- a dirty, blocked, damaged or misaligned sensor
- bends, crests and unusual road geometry
- vehicles cutting in suddenly
- small, low, stationary or unusually shaped objects
- pedestrians or cyclists outside the system’s detection conditions
- trailers, loads or accessories that affect sensors
A system can be temporarily unavailable without an obvious hardware failure. Conversely, the absence of a warning light does not prove that every sensor, mounting position or system input is correct.
Never test it by creating a hazard
Do not drive toward a person, vehicle, wall or improvised target to test AEB. Professional testing requires the correct soft targets, controlled site, measurement equipment and manufacturer procedures.
When braking is unexpected
An apparent false intervention is often called phantom braking. Use the first-response guide to keep control first, record useful evidence only when safely parked and decide when the event needs escalation. Repeated, severe or post-repair events need systematic inspection.
Repairs and calibration
Windscreen, bumper, grille, body, suspension or wheel-alignment work may disturb inputs used by AEB. Calibration is not automatically required after every job, but the current manufacturer repair procedure must be checked.
Key point
AEB is a valuable last layer of assistance, but it does not replace observation, spacing and timely driver braking.
Sources reviewed
- Driver Assistance TechnologiesNational Highway Traffic Safety Administration · United States; general principles · Accessed September 5, 2026
- Advanced driver assistanceInsurance Institute for Highway Safety · United States; research and general principles · Accessed September 5, 2026
- UN Regulation No. 152, Revision 2United Nations Economic Commission for Europe · UNECE contracting parties; regulatory context · Revision 2 · Accessed September 5, 2026